1. Field of the Invention
The present invention relates to an environmentally improved energy absorbing, damping and blocking sound barrier composite which replaces lead and other synthetic barriers and the process for making same. More particularly, the present invention relates to sound attenuation composites having a dense, resilient, elastic polymer barrier layer and a dense, resilient, elastic fractured open cell foam layer formed in one process.
2. Description of the Related Art
Sound absorption barriers have been utilized to reduce noise levels in work areas, such as, areas having manufacturing machinery and construction equipment. Sound barrier materials have been made by incorporating sound blocking heavy particles into polymer binders. For example, U.S. Pat. No. 4,110,510 to Oliveira discloses a sound barrier material with a polyvinyl chloride impregnated mesh sheet having a coating of a chlorinated polyethylene containing barium sulfate. The concentration of barium sulfate in the chlorinated polyethylene binder is 50-200 parts of barium sulfate in each 100 parts of chlorinated polyethylene. This coated sheet is laminated to two sides of an intermediate foam layer to form the sound barrier.
U.S. Pat. No. 4,818,603 to Mueller discloses a thermal-acoustic insulating material which is fabricated by bonding a thin heavy metal-loaded polyorganophosphazen septum to the surface of a foamed polyamide insert. As another example, U.S. Pat. No. 4,367,259 to Fulmer et al. discloses a sound deadening material which is obtained by mixing sound dampening materials with water and bonding them together by adding a water-miscible isocyanate-terminated prepolymer which reacts with the water to form a crosslinked binder.
The present invention provides a sound attenuation composite having superior sound absorption, damping and blocking characteristics and accomplishes these tasks with an extremely lightweight construction. In particular, a sound attenuation composite is provided having superior sound attenuation characteristics at low cost and at approximately one half the weight in comparison to known sound barriers, e.g., a lead sheet.